N498TBCessna T210M

On March 25, 2024, about 1100 central daylight time, a Cessna T210M airplane, N498TB, was substantially damaged when it was involved in an accident near San Saba, Texas. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

According to the pilot, during a cross-country flight, the engine manifold pressure started to decrease slowly. The pilot elected to divert and started a descent for a precautionary landing. During the descent, the oil pressure gauge went to zero and the propeller began to overspeed. The pilot had the airport in sight when smoke began to exit the engine cowling as he aligned the airplane with the runway for landing. The pilot lowered the landing gear but kept the flaps retracted as the airplane approached the aerodynamic stall speed. The pilot landed the airplane about 100 yards short of the runway in wet grass. The landing gear dug into terrain and the airplane came to rest inverted, resulting in substantial damage to the fuselage and wings.

After the pilot egressed from the airplane, he noticed a small fire near the engine compartment. He used a handheld fire extinguisher to suppress the engine compartment fire.

The airplane was equipped with a digital engine monitor. A review of the recovered engine data revealed that, about 37 minutes into the flight, the engine oil pressure began a steady decrease while the airplane altitude remained about 11,000 ft. The engine’s manifold pressure, fuel pressure, and fuel flow values remained unremarkable until about 1 hour 7 minutes into the flight, when the oil pressure decreased briefly to 22 psi. The airplane remained at 11,000 ft until about 1 hour 16 minutes into the flight, when the oil pressure decreased to as low as 3 psi. As the airplane’s altitude rapidly decreased, the engine rpm briefly increased from 2,500 rpm to about 4,100 rpm. For the remainder of the flight, the oil pressure fluctuated between 4 and 18 psi, the manifold pressure fluctuated between 10 and 18 inches of mercury (inHg), and the engine rpm steadily decreased. About 1 hour 19 minutes into the flight, the final recorded data indicated 8 psi oil pressure, 28.6 inHg manifold pressure, 386 rpm, 4.9 gallons per hour fuel flow, 1.4 psi fuel pressure, and altitude 1,254 mean sea level (about 20 ft above ground level).

The airplane had been modified by a supplemental type certificate for the installation of a turbo-normalized Continental IO-550-P engine. A postaccident examination of the engine found several holes on the top of the engine crankcase. The engine was seized and could not be rotated. During disassembly of the engine, metal pieces of various sizes were located throughout the oil system. Examination of the oil pump did not find any blockages, and the pump exhibited signatures of rotational scoring. Multiple connecting rods were found damaged and separated, but their respective bearings were not identifiable and, as such, could not be examined. The engine disassembly revealed several areas of thermal distress consistent with a lack of oil lubrication. Examination of the turbocharger did not detect any anomalies.

A small amount of oil was observed within the engine during disassembly; however, there was not a substantial amount of oil seen on the engine, firewall, cowling, or fuselage. Besides the holes in the upper engine crankcase, the examination of the engine did not identify another oil leak source.

The pilot reported that the day before the accident, he changed the engine oil and added 9 quarts of oil.